Can't find proper use of objectfield in a custom editor window (C#)

The unity documentation page only has java, and there were 2 errors on line 22. Sorry for such a noob question.

error CS1503: Argument #1' cannot convert object' expression to type UnityEngine.Rect' error CS0119: Expression denotes a type', where a variable', value' or `method group' was expected

 using UnityEngine;
 using System.Collections;
 using UnityEditor;
 
 public class roommanager_window : EditorWindow
 {
 
     public static roommanager_window window = null;
 
     public GameObject rooms = null;
 
 
     public static void Init()
     {
         window = (roommanager_window)EditorWindow.GetWindow(typeof(roommanager_window), false, "room mngr");
     }
 
     void OnGUI()
     {
         GUILayout.Label("Base Settings", EditorStyles.boldLabel);
 
         rooms = EditorGUI.ObjectField(Rect(3, 3, position.width - 6, 20), "Rooms:", rooms, GameObject);
     }
 }